tree-wide: use IN_SET macro (#6977)

src/basic/env-util.c

@@ -707,7 +707,7 @@ char **replace_env_argv(char **argv, char **env) {
         STRV_FOREACH(i, argv) {
 
                 /* If $FOO appears as single word, replace it by the split up variable */
-                if ((*i)[0] == '$' && (*i)[1] != '{' && (*i)[1] != '$') {
+                if ((*i)[0] == '$' && !IN_SET((*i)[1], '{', '$')) {
                         char *e;
                         char **w, **m = NULL;
                         unsigned q;